1. Field of the Invention
The invention relates to an improved structure for opening or closing a valve to control fluid flow therethrough in response to an earthquake.
2. Description of the Prior Art
After a sizable earthquake damage can be expected due to escaping water or flammable gas from ruptured pipes and pipe joints in residential and commercial buildings. Valves are known which respond, for example, to pressure differentials to seal off automatically the gas or water line if it should break. Such valves, however, do not respond to minor leaks such as might be expected at pipe fittings. Numerous other valves are known which are provided with mechanical relief structures for automatically sealing a pipe in response to seismic vibrations. The known release mechanisms suffer from a variety of drawbacks, such as complexity of construction, degeneration in the ability to respond after long periods of non-use, inconvenience in resetting the release mechanism, and oversensitivity to small vibrations. A particular drawback of the known release structures is the limited reliability with which they will respond to vibrations of a predetermined magnitude.